Powered pallet conveyors are known and are conventionally utilized for the transport of pallets and containers between a high bay warehouse and consignment bases or for loading and unloading of trucks and trailers with pallets or containers. Powered pallet conveyors comprise a vehicle and a rail system which defines the pathways on which the vehicle should travel.
Conventional rail systems for a powered pallet conveyor may comprise switches for allowing the vehicle to travel on alternative pathways. U.S. Pat. No. 4,498,399 discloses a special switch arrangement for a conveying appliance. In the prior art two further types of switches are known, namely a quadro-switch and a rotation switch.
A quadro-switch, as shown in FIG. 4, is positioned by initially bringing the pivotable wheels of the vehicle to a stop on rail portions rotatable in a plane level with the ground, wherein the pivotable wheels are pivotable about an axis perpendicular to ground level. Subsequently the rotatable rail portions are rotated so that the wheels of the vehicle are oriented along and guided to the new travel pathway. This process requires that the vehicle stops on the switch during the positioning process, such that the positioning of the switch delays the transport process.
A rotation switch, as shown in FIG. 5, is likewise operated by first positioning the vehicle on the switch, so that the vehicle can be rotated as a whole on a rotatable turntable.
Subsequently the rotatable turntable is rotated, so that the vehicle is oriented along and guided to the new travel pathway.
Both switches are unsatisfactory in so far as the vehicle cannot travel continuously across the switching means without stopping in between. As a consequence the employment of a conventional switch results in a limitation of the maximum speed which the powered pallet conveyor can fulfill a conveying task. The limitations imposed by the switch increase in proportion to the number of switches employed in the pathway.
Furthermore, conventional switching means have considerable space requirements. Moreover, vehicles which are subjected to frequent acceleration/deceleration suffer from increased wear, so that high maintenance costs occur.